High levels of sulfate detected in two wells
Not a major health risk, but does affect quality

GREEN VALLEY--Does your tap water taste salty? Is it colored and overly hard? Does it stain your glasses?

Green Valley's Community Water Co. recently discovered high concentrations of sulfate and Total Dissolved Solids (TDS) in at least two of its wells, the likely result of seepage from Phelps Dodge's Sierrita Mine tailings (the dross remaining after the mining process).

According to a report released this week by the Green Valley Community Coordinating Council's Environmental Committee, sulfate and TDS levels in the ground water in Community Water's western Green Valley service area have increased gradually between 1995 and 2003, and are now much higher than the "background" levels at which they normally occur.

"Clearly, the water received by at least some people in the Community Water service area has had noticeably poor aesthetic properties since 1995, and these aesthetic properties have continued to degrade," wrote Allan MacDonald, who, as chair of the GVCCC Environmental Committee and a retired environmental consultant, prepared the report.

"Also, this degradation was not sudden, but occurred over a period of several years."

Since August, the GVCCC, Community Water, and Phelps Dodge Sierrita's Environmental Department have been working on a solution to the sulfate and TDS problems, which all parties agree do not pose a major health risk, but do affect the look, taste, and overall quality of the area's groundwater.

Seeping for decades

Mike Wood, of the Phelps Dodge Sierrita Environmental Department, said Friday that the mining concern recognizes that sulfates have been seeping into the groundwater in western Green Valley "for decades."

"When you have tailings, there is really no way around having a high concentration of sulfates," Wood said.

Wells 7 and 8

Community Water Co. serves about 15,500 people out of four wells. Two of those, Wells 7 and 8, are located west of La Canada Road in Green Valley.

The Green Valley community water system is based on gravity flow and the affected wells are at a high elevation. They have the capability to feed the entire water system, according to Mike Weber, head of Community Water. Depending on which wells are operating at any particular time, water from Wells 7 and 8 can go throughout the system, he said.

The GVCCC report says that Wells 7 and 8 have shown increasing concentrations of sulfate and TDS since they were drilled in 1982 and 1994, respectively.

Using less than 100 milligrams per liter as an acceptable background concentration for sulfates, and 300 mg/L for TDS, MacDonald found that Well 7, located about two miles north of Well 8, recorded an increase in sulfate concentrations from an average of 70 mg/L in 1995 to an average of 452 mg/L in 2003.

TDS levels in Well 7 were less than 300 mg/L (background level) until 1996, when they began to increase.

Concentrations increased

By the end of 1998, TDS concentrations had increased to 500 mg/L, and by the 2003 had reached at least 800 mg/L.

Sulfate concentrations increased in Well 8 from 250 mg/L at the end of 1996 to 500 mg/L in early 2003. Similarly, TDS levels in Well 8 increased from around 300 mg/L in mid-1996 to nearly 900 mg/L in early 2003.

Such increases in sulfate and TDS concentrations in Wells 7 and 8 provide "evidence that contaminants are present in the aquifer(s) (at Wells 7 and 8)" MacDonald wrote in the report.

Is it dangerous?

The federal Environmental Protection Agency, working with the Centers for Disease Control, this year came out with a joint report, the product of several years of research, recommending that sulfates and TDS in drinking water not be subject to regulation under the Safe Drinking Water Act.

The EPA has developed what it calls Secondary Maximum Contaminant Level (SMCLs) guidelines, however, meant to be used as thresholds for contaminants not considered a health threat but still deemed adverse to overall water quality.

The SMCL for sulfate is 250 mg/L, and for TDS it is 500 mg/L.

Using those federal guidelines, the water in Wells 7 and 8 exceeds by a large margin what is considered acceptable for both sulfate and TDS.

May develop diarrhea

At these levels there is a small risk that some people not acclimated to the water will develop acute diarrhea, MacDonald said.

Some people, especially the very young and the very old who use formulas or powdered nutritional supplements, could become sicker than others.

But, MacDonald said, in the majority of cases people acclimate to the high concentrations of sulfate and TDS in the water within a week or two of first drinking it, and thus no longer suffer adverse reactions.

There are also several aesthetic problems that the high concentrations cause, including a salty taste, hardness, deposits, colored water, and staining, MacDonald said.

While the federal guidelines are not enforceable, and technically neither Community Water nor Phelps Dodge has to do anything to clean up the sulfate and TDS concentrations in the water, both companies have begun to look into ways to reduce the contaminants.

"We are always eager to supply the highest quality product to our customers," said Community Water's Weber.

"We are working quite closely with PD, who to their credit have so far displayed a willingness and a desire to mitigate the sulfate and incur the cost for the fix."

Two options

At a meeting of the GVCCC Environmental Committee Friday, PD's Wood said that the mine and the water company have identified "two long-term solutions" to the water problem.

One, Wood said, is for PD to find higher quality water in its own wells and make it available to Community Water to put into service. The other option is for PD to install a new well for Community Water outside the impacted area, Wood said.

Both options could be a long time coming, however, as water regulation in Arizona is typically a long and Byzantine process.

"We are pursuing this with all due speed," Wood said Friday. "But there is a lot of regulation involved; this will take us several months to work through."

Meantime, PD and Community Water are working on a quicker, short-term option that could have cleaner drinking water on the west side within the month, Wood said.

PD will pay cost

It is unclear as yet how much all of this is going to cost, but it is not likely to impact Community Water's rates, CW's Weber said, as PD has so far agreed to pick up the tab.

Peter Faur, a Phelps Dodge spokesman in Phoenix said Monday that the mining company doesn't know how much it is going to cost, and that it is too early in the process even to make an estimate.

thull@gvnews.com | 625-5511 x 22